Grey water

Grey water

Re-use waste water

Grey water is the waste water that comes from your washing machine, shower or bath. It is not suitable for drinking and the cleaning products that are washed down the drain may harm the environment. However, when grey water is collected safely, it can be used to irrigate lawns and gardens.

Using waste water from kitchen sinks and dishwashers is not recommended unless it is chemically treated as it contains high levels of fat, grease and food remains that can clog soils and create unwanted smells.

Advantages of grey water re-use

  • Human bacteria found in grey water when we wash is digested by organisms in the soil.
  • Cleaning product particles are broken down and aborbed by plants.
  • Helps to preserve drinking water which is a precious resource.
  • Reduces the amount of water and sewage diverted to oceans and rivers.
  • Helps to reduce water bills.
  • Ensures gardens are watered in dry periods.

Ways to re-use grey water

Manual collection: Small amounts collected from washing machine or shower to immediately water plants.

Grey water diversion device: The device redirects untreated water to irrigate lawns or gardens through underground drainage at least 10 cm below the surface. The device is controlled by a tap or switch that will flush the water away to a sewer when it is not required. You won’t need City of Sydney approval if the device has a WaterMark licence. Diversion devices must be installed by a licensed plumber.

Grey water treatment systems: More advanced than a diversion device, these systems collect and disinfect grey water which can then be used to irrigate gardens, flush toilets and in washing machines. You will need permission from the City to use a treatment system and it must be fitted by a licensed plumber.

Tips for safe grey water use

  • Use only on plants that humans won’t eat or touch.
  • Use only second rinse water.
  • Don’t use water that has washed nappies.
  • Make sure grey water does not pool on the ground surface.
  • Don’t over water plants.
  • Use grey water within 24 hours.
  • Don’t use when residents are sick.


City of Sydney
02 9265 9333


NSW Office of Water: Grey water

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Last updated: Monday, 20 January 2020